FBH The end of the SAGA ?

[FrenchMike]

Originally Posted by cb750chris

Hi, just to ressurect an old thread.
I am trying to get a FBH running on an MGZT. It is a retrofit unit (if that makes any difference)
I have installed the fuel pump that is needed, and this works (checked by supplying 12V to pin 6) of the heater.
The fault is that the fan runs for about 3 seconds, then pauses for about 4 seconds, then the fan runs for about 2 mins.

I have checked the 47K Ohm, and the 4.7K Ohm resistors (the 47 K Ohm meters up at 49.8 K Ohm, so should be ok?

The other things I have checked are that, on initial start up, the glow plug gets a puse of power, but then no more power is supplied. There is no drive sent to the fuel pump.
I have tried swapping the PCB with a friend, and the problem follows the PCB (suggesting the car "services" are ok, it is the PCB that is faulty)

There is a "suspicious" looking surface finish on the item that fegyvej highlighted (in post #63), next to the 47KOhm resistor. This item looks corroded / burned. This item goes between a power pin, and pin 6(?) of the elmos device (counting clockwise from the 1/2 moon orientation marker)

Any suggestions where to look next?

Thanks
Chris

Hi,the first component is a capacitor and the second a one ohm resistor.

If you have checked all the resistors,remains the Elmos component..

Mike

[dj_lyw]

Hello everyone! I have a picture with my FBH and I tested all resistors under that troublesome glued paste and everything ok, except of a green electronic piece that my multimeter read infinite. It looks like a resistor but nothing wrote on it(if it's a capacitor pls tell me what is the value). I will attach a picture with that component and pls tell me what it is(that circled and it is on pin 6 of ELMOS 10026B). Thanks in advance!

[mashby]

Originally Posted by FrenchMike

MY STORY:

I came upon this Forum 3 years ago after my in tank fuel pump broke.
I found advice here to have my pump quickly and cheaply repaired.

I too also had the strange Fuel Burning Heater (FBH) behaviour caused by the K bus.
(Which I have since disconnected.)

As a regular reader, I have noted lots of threads about FBH issues and in particular
that the PCB was reported as being non repairable.

The cold days made me inclined to study the question. I began by trying to collect information about the circuit diagram etc, (not very easy)

At first I thought the Interface IC bus was the culprit.
I ordered the genuine interface IC bus (ELMOS 10026B) from Hong-Kong,
but one month later, nothing ;they forgot to ship
Meantime, I bought the Riesler interface Bus describe by Keith Alexander .
I discovered than his Interface Bus IC was a (Melexis TH3122) similar
and more easy to get.

Next, I built up a test bench and established communication between my laptop and
the Webasto PCB.
However, there was a combustion air fan error. (running at max speed).
Tracing the PCB ‘tracks’, I discovered than the power Mosfet’driver was always
ON although the Micro bus line concerned was live .The link is in fact a SMD (surface mounted) resistor well hidden under a kind of sticky sealant (looks like meringue.)
The resistor was marked 4.75 kOhms but my multimeter showed infinite !
Strange ,I had rarely seen that before in my professional live.

Anyway, I quickly replaced it and …..everything worked …..

I opened a new thread on the forums to tell the news.

So, the only possible cause, was that the resistors were being attacked by a chemical agent from that paste (meringue).

(can you imagine how many Webastos this may have affected all over the world !!)

I would like to freely publicise this valuable information, in the true spirit of the ‘Forum’ and it’s ethos of sharing information.

Most members will be able to do the work for themselves ( or know a man that can!).
However, I can do the repair for others who don’t feel like tackling the job themselves

TOOLS NEEDED:

Low power soldering iron with thin tip correctly earthed.
Table magnifier,
Solder
SM (surface mounted) resistors 4.7 Kohm ; 47Kohm


PROCEDURE

Extract the PCB from the FBH (5 screws)

Pic 1


Remove that sticky white paste and clean the area to show the resistors.
Take a measurement of them: two 4.75 Kohm and one 47 Kohm.


Pic2



If possible, built a test bench for checking out all the parameters before fitting on car.

Pic3



Results

Pic4



Enjoy your warmer car :lol:

Mike

Mike,

I have a 2005 E53 with a erratic running combustion fan motor. It will start OK run for about 2 minutes then run erratically & shut down with INPA message Fan interruption. Have read about faulty 4.7k resistors in PCB but could it be clogged combustion chamber causing flame out? Can you repair BMW PCD's. I am capable of changing resistors but don't want to start until sure that fault is PCB?

Would appreciate your thoughts

Mark A

[FrenchMike]

Hi Mark,

You have to know that i can't test entirely the BMW one's for the cycle is
depending on the Kbus 'car.

I only can test the driving of the external components .and read the recorded
errors.

The Rover's are more easy to test ..

However,i can still have a look

Mike

[cowmanmick]

my fbh wont fire up it runs but doesnt fire is it the pcb i would like french mike to have a look at it have anyone got a contact address for him ,or can mike please contact me himself,i would be apreciated for any help

[klarzy]

Originally Posted by cowmanmick

my fbh wont fire up it runs but doesnt fire is it the pcb i would like french mike to have a look at it have anyone got a contact address for him ,or can mike please contact me himself,i would be apreciated for any help

just click on his name and send him a PM....

[wolfdoguk]

Hi, and happy new year to everyone. My first post after being a member for ages, apart from P.Ming big russ and having him remap 2 ecu's. I don't really want to impose on the good people here, but I feel I need some answers from the boffins here! I have ploughed through endless threads and posts, but just got mesmerised, so I hope it's ok to post here!

I have a unhealthy obsession with fbh's, especially after reading the endless information on this site about them, and past experience with cab heaters in my trucks!
I have one already fitted to my saloon, but I bought one complete with pump, and retro- fitted it to my 52 plate tourer.
As soon as I put fuse 8 in, the fan motor burst into life and ran a few seconds. I couldn't get it to run at all after that, it was dead, tried resetting it by removing the fuse, but still nothing on earthing pin 6. I replaced the fuse a day or so later and it fired up and ran! I was a happy chappy! However, after a week it just started running the fan and the water pump, but it just wouldn't fire. I tried resetting again, but nothing.
I have a perfectly good one, which I know works on my 75 saloon, swapped them round, it did the same thing when connecting the battery to the saloon, only this time it burst into life, only to cut out and just run the fan, blowing cold air out of the exhaust and circulating water. Fired up the known good one on the tourer (originally off the saloon) and it worked perfectly!!..... For a week.... Now, Monday, that one has started the same game!! Although, this one doesn't start running on connecting the fuse, symptoms are the same, i.e. running the fan (a little faster than usual) and water pump, but not firing!I also bought 2 gsm's off ebay after reading all about them on here, but they aren't without their faults either!! one doesn't quite work as it should, although, i have no instructions apart from what's on the listing and what i can squeeze out of the guy by asking! and the other didn't work at all!!!!I also fitted the maplin relay on the heater
too, as done by another excellent life-saving-member, it was lovely while i had it all working "to a fashion"! Now, someone mentioned that they aren't very good as anchors or doorstops, but I'm liking the idea of donning my steel toe cap boots and launching them like rugby balls, or, a splash of petrol and a match to activate them....I hope the other genius aka FrenchMike reads this, because, surely it would be an unlikely coincidence that both pcb's fail, and in the same way in such a short time? unless it's something that is blowing the resistors, but there's only the 5c temp wire, dosing pump and pin 6 earth activator fitted, the k-bus is disconnected.On another note, i removed the first pcb, cleaned off the gum around the capacitors and found the furthest right one was black on where it had sat on the resistors I also took out the pcb for the other fbh, but surprisingly, this one is almost charred under the blob of gum,on the right of the pcb. Now, another God "HarryM1BYT" shows a picture of a different resistor marked as one of the" failers" to what FrenchMike shows in his picture, unless I'm looking at it wrong, but does anyone know what type the other resistors are and what size they are in that area on the board, under the blob? and what particular size they are, ohm, wattage and physical size etc, or doesn't it matter? if a reading can't be found with a multimeter (i just bought a new one, and both my old one and new one don't show any readings, as if they are open circuit, so how do we know what to replace them with?! i'm not a big electrical wizzard, in fact i've never tackled anything as small and fiddly as these resistors) I've just ordered a table magnifier in the hope of doing these myself....
Even "if", by some miracle I get them fixed, I'll still be worried about putting it back on the car in case it blows again!
I've attached a couple of pictures of the bought pcb (first one to snuff it) which seems to show one of the offending resistors looking suspect and the pcb from the known good one (well, was a good one...) Showing the charred area around the right hand capacitor where the gum was.
Any pointers and/ or ideas would be gratefully received.

Thank you very much!
Paul

[Stephen Davies]

finally got one working on the bench, 47K resistor had gone bad, replaced with one of Maplin's last resistors, and its all working, very impressed with its heat output, even stuck an old central heating radiator on it, this could do a fine job of heating the workshop, now to attack the one in the car, now that i know what i'm doing

[HarryM1BYT]

Originally Posted by Stephen Davies

finally got one working on the bench, 47K resistor had gone bad, replaced with one of Maplin's last resistors, and its all working, very impressed with its heat output, even stuck an old central heating radiator on it, this could do a fine job of heating the workshop, now to attack the one in the car, now that i know what i'm doing

l

Frenchmike very kindly explained how to repair these FBH PCB's, so you can fix your own and I am sure you are not thinking of doing it - but it would be very unfair to begin repairing other's FBH PCB's.

[sln8458]

Originally Posted by Stephen Davies

finally got one working on the bench, 47K resistor had gone bad, replaced with one of Maplin's last resistors, and its all working, very impressed with its heat output, even stuck an old central heating radiator on it, this could do a fine job of heating the workshop, now to attack the one in the car, now that i know what i'm doing

These heaters are used on narrow boats for heating and hot water!
I considered using one to heat the garden room (shed )

Steven